In-riser hydraulic power recharging

ABSTRACT

A method for pressurizing a hydraulic accumulator includes creating an annulus pressure zone in hydraulic communication with the hydraulic accumulator through a hydraulic recharging circuit and applying a hydraulic pressure to the annulus pressure zone. Operating the hydraulic recharging circuit in response to applying the hydraulic pressure and pressurizing the hydraulic accumulator in response to operating the hydraulic recharging circuit.

RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No.61/583,634 filed on Jan. 6, 2012.

BACKGROUND

This section provides background information to facilitate a betterunderstanding of the various aspects of the disclosure. It is to beunderstood that the statements in this section of this document are tobe read in this light, and not as admissions of prior art.

Offshore systems (e.g., lakes, bays, seas, oceans etc.) often include ariser which connects a surface vessel's equipment to a blowout preventerstack on a subsea wellhead. Offshore systems which are employed for welltesting operations also typically include a safety shut-in system whichautomatically prevents fluid communication between the well and thesurface vessel in the event of an emergency. Typically, the safetyshut-in system includes a subsea test tree which is landed inside theblowout preventer stack on a pipe string. The subsea test tree generallyincludes a valve portion which has one or more safety valves that canautomatically shut-in the well via a subsea safety shut-in system.Hydraulic and electrical power to actuate the valves and devices of thesubsea test tree is often communicated from the surface vessel by anumbilical.

SUMMARY

In accordance to one or more embodiments, a method for pressurizing ahydraulic accumulator includes creating an annulus pressure zone inhydraulic communication with the hydraulic accumulator through ahydraulic recharging circuit and applying a hydraulic pressure to theannulus pressure zone. The hydraulic recharging circuit is operated inresponse to applying the hydraulic pressure and the hydraulicaccumulator is pressurized in response to operating the hydraulicrecharging circuit.

An embodiment of a subsea well system includes a riser extending from awater surface to a blowout preventer stack located at a wellhead at aseafloor, a subsea tree landed in a bore of the blowout preventer stackon a landing string extending through the riser, a hydraulic power unitconnected within the landing string, the hydraulic power unit having aclosed loop hydraulic control circuit extending from a hydraulic supplyaccumulator through a hydraulically actuated device to a hydraulicreservoir, and a hydraulic recharging circuit hydraulically connectedbetween the closed loop hydraulic circuit and an annulus pressure zonecreated in the blowout preventer stack. The hydraulic recharging circuitpressurizes the hydraulic accumulator in response to a hydraulicpressure applied to the annulus pressure zone.

An example of a method for recharging hydraulic power in a subsea wellsystem in accordance to one or more embodiments includes creating anannulus pressure zone in a blowout preventer stack. The subsea wellsystem may include a riser extending from a water surface to the blowoutpreventer stack located at a wellhead at a seafloor, a subsea treelanded in the blowout preventer stack on a landing string extendingthrough the riser, a hydraulic power unit connected with the landingstring and having a closed loop hydraulic control circuit extending froma hydraulic supply accumulator through a hydraulically actuated deviceto a hydraulic reservoir, and a hydraulic recharging circuithydraulically connected between the created annulus pressure zone andthe closed loop hydraulic control loop. The method includes applying ahydraulic pressure to the annulus pressure zone, operating the hydraulicrecharging circuit in response to the applied hydraulic pressure, andpressurizing the hydraulic supply accumulator in response to operatingthe hydraulic recharging circuit.

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofclaimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of in-riser hydraulic power recharging devices and methodsare described with reference to the following figures. The same numbersare used throughout the figures to reference like features andcomponents. It is emphasized that, in accordance with standard practicein the industry, various features are not necessarily drawn to scale. Infact, the dimensions of various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 illustrates an example of a subsea well system in whichembodiments of in-riser hydraulic power recharging devices and methodscan be implemented.

FIG. 2 is a schematic diagram of a subsea well system in accordance withone or more embodiments.

FIG. 3 is a schematic diagram of a subsea well system in accordance withone or more embodiments.

FIG. 4 is a schematic diagram of an example of an in-riser hydraulicpower recharging system in accordance to one or more embodiments.

FIG. 5 is a schematic diagram of an example of an in-riser hydraulicpower recharging system in accordance to one or more embodiments.

FIG. 6 is a schematic diagram of an example of an in-riser hydraulicpower recharging system in accordance to one or more embodiments.

FIG. 7 is a schematic diagram of an example of an in-riser hydraulicpower recharging system in accordance to one or more embodiments.

FIG. 8 is a block diagram illustrating an example of an in-riserhydraulic power recharging method in accordance to one or moreembodiments.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the disclosure. These are, of course,merely examples and are not intended to be limiting. In addition, thedisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

As used herein, the terms “connect”, “connection”, “connected”, “inconnection with”, and “connecting” are used to mean “in directconnection with” or “in connection with via one or more elements”; andthe term “set” is used to mean “one element” or “more than one element”.Further, the terms “couple”, “coupling”, “coupled”, “coupled together”,and “coupled with” are used to mean “directly coupled together” or“coupled together via one or more elements”. As used herein, the terms“up” and “down”; “upper” and “lower”; “top” and “bottom”; and other liketerms indicating relative positions to a given point or element areutilized to more clearly describe some elements. Commonly, these termsrelate to a reference point as the surface from which drillingoperations are initiated as being the top point and the total depthbeing the lowest point, wherein the well (e.g., wellbore, borehole) isvertical, horizontal or slanted relative to the surface. In thisdisclosure, “hydraulically coupled,” “hydraulically connected,” andsimilar terms, may be used to describe bodies that are connected in sucha way that fluid pressure may be transmitted between and among theconnected items.

FIG. 1 illustrates an example of a subsea well system 100 in whichembodiments of in-riser hydraulic power recharging systems 10 can beimplemented. Subsea well system 100 includes a vessel 102 which ispositioned on a water surface 104 and a riser 106 which connects vessel102 to a blowout preventer (“BOP”) stack 108 on seafloor 110. A well 112has been drilled into seafloor 110 and a tubing string 114 extends fromvessel 102 through riser 106 and through blowout preventer stack 108into well 112. Tubing string 114 is provided with a bore 116 throughwhich fluids (e.g., formation fluid, drilling fluid) can be conductedbetween well 112 and surface 104. Although vessel 102 is illustrated asa ship, vessel 102 may include any platform suitable for wellboredrilling, production, or injection operations.

A subsea tree 120 is landed in blowout preventer stack 108 on the upperportion of tubing string 114, referred to herein as landing string 132.A lower portion 119 of tubing string 114 extends into well 112 and issupported by a tubing hanger 121 that is landed in wellhead 136. Subseatree 120 includes valve assembly 124 and a latch 126. Valve assembly 124may act as a master control valve during testing of well 112. Valveassembly 124 may include one or more valves (i.e., hydraulicallyactuated devices), such as flapper valve 128 and a ball valve 130. Latch126 allows landing string 132 to be disconnected from subsea tree 120,for example during an emergency shutdown. Retainer valve 133 is arrangedat the lower end of landing string 132 to prevent fluid in the upperportion of tubing string 114 from draining into the subsea environmentwhen the landing string is disconnected from subsea tree 120. It shouldbe clear that the embodiments are not limited to the particularembodiment of subsea tree 120 shown, but any other valve system thatcontrols flow of fluids through tubing string 114 may also be used. Anexample of a subsea tree that may be utilized is disclosed in U.S. Pat.No. 6,293,344.

Blowout preventer stack 108 includes pipe rams 138, shear rams 140, andannular rams 142. BOP stack 108 defines a passage 143 for receivingtubing string 114. Subsea tree 120 is arranged within blowout preventerstack 108, and retainer valve 133 extends from subsea tree 120 intoannular rams 142. With additional reference to FIG. 2, external fluidcommunication with passage 143 of BOP stack 108 is provided through BOPaccess lines 144, 146, which are illustrated extending along theexterior of riser 106 in FIG. 1. The BOP access lines may be referred toindividually as kill and choke lines. Drilling fluid 26 (FIG. 2) can bepumped for example via fluid system 5 into the BOP stack 108 via BOPaccess line 144, for example, and fluid 26 can be removed from the BOPstack 108 via BOP access line 146, for example.

Subsea well system 100 includes a safety shut-in system 118 whichprovides automatic shut-in of well 112 when conditions on vessel 102 orin well 112 deviate from preset limits. Safety shut-in system 118includes subsea tree 120 and a subsea control system 12 to operatevarious hydraulically actuated devices of subsea tree 120 such as, andwithout limitation, valves 128, 130, retainer valve 133 and latch 126.Subsea control system 12 can be utilized to operate, for example, valves128, 130 during well testing or other production or injection operationsas well as during emergency shutdown. In the illustrated embodiment,subsea control system 12 is a modular unit that includes a subseahydraulic power unit 14 (e.g., accumulators, pumps, valves, hydrauliccircuits) to operate the hydraulic device actuations of subsea tree 120control systems, safety valves 128, 130, latch 126, tubing hanger 121,and other downhole valves and control systems. The modular units can beconnected within landing string 132 to form a continuous axial bore 116between vessel 102 and well 112. Hydraulic power unit 14 may comprise aclosed loop hydraulic control circuit between pressurized hydraulicaccumulators (i.e., supply accumulators), hydraulic reservoirs and thehydraulically actuated devices. A hydraulic accumulator refers to ahydraulic device that is able to store potential energy that whenreleased provides hydraulic activation pressure to enable actuation of ahydraulically operated device. Subsea control system 12 may includeelectrical system 16 (e.g., batteries, processors, electrical circuits)for example deployed with hydraulic power unit 14.

Techniques and devices disclosed herein may be used in cooperation withexisting components and control systems. For example, embodiments ofin-riser hydraulic power recharging systems 10 may be employed with theSenTURIAN Deep Water Control System manufactured by SchlumbergerCorporation and the SenTURIAN Subsea landing string electrohydraulicoperating system. Non-limiting examples of subsea control system 12 andhydraulic power unit 14 are described in U.S. publication 2011/0120722and U.S. publication 2011/0005770, which are incorporated by referenceherein.

Each hydraulic device actuation reduces the available hydraulic supplypressure of subsea hydraulic power unit 14. Embodiments of subsea wellsystem 100 include in-riser hydraulic power recharging system 10 inhydraulic communication with hydraulic power unit 14 to recharge thehydraulic pressure of one or more hydraulic accumulators. Recharginghydraulic power unit 14 includes pressurizing one or more hydraulicaccumulators.

According to some embodiments in-riser hydraulic power recharging system10 is in hydraulic communication with a BOP access line, for example,BOP access line 144, to recharge the hydraulic pressure supply ofhydraulic power unit 14. For example, in-riser hydraulic powerrecharging system may be in hydraulic communication with an annuluspressure zone 18 created in BOP stack 108 (see, e.g., FIGS. 2, 3), forexample by closing one or more of the blowout preventer rams 138, 142,from which hydraulic pressure can be harvested for operating in-riserhydraulic power recharging system 10. According to embodiments,hydraulic power unit 14 can be recharged without being connected to anumbilical extending from surface 104 for example or by connection with aremote operated vehicle.

For example, with reference to FIG. 2, a BOP annulus pressure zone 18 isillustrated created in BOP passage 143 between a closed annular ram 142and a closed pipe ram 138 and between landing string 132 (i.e., subseatree 120) and BOP stack 108. In-riser hydraulic power recharging system10 may be in hydraulic communication with BOP annulus pressure zone 18for example through hydraulic supply port 20 and hydraulic conduit 22.Hydraulic power unit 14 may include for example one or more hydraulicsupply accumulators 34 and a hydraulic reservoir 36. Hydraulic reservoir36 may be spring biased (i.e., pressurized fluid, mechanical spring) tobe above hydrostatic pressure if it is desired for the hydraulicreservoir to be positive pressurized. BOP access line 144 may be opened,for example opening valve 24, to communicate fluid 26 (i.e., drillingfluid) from fluid system 5 (FIG. 1) through BOP access line 144 to thecreated BOP annulus pressure zone 18. Valve 28 in BOP access line 146 isclosed allowing hydraulic pressure to build in annulus pressure zone 18to operate in-riser hydraulic power recharging system 10. Hydraulicpressure in BOP annulus pressure zone 18 can be communicated throughport 20 and hydraulic conduit 22 to pressurize at least one hydraulicsupply accumulator 34 of hydraulic power unit 14. BOP access line 146may be opened at valve 28 to relieve the hydraulic supply pressure inannulus pressure zone 18.

A non-limiting example for harvesting hydraulic pressure to rechargehydraulic power unit 14 is described with reference to FIG. 3. Hydraulicpower unit 14 may include for example one or more hydraulic supplyaccumulators 34 and hydraulic reservoirs 36. Hydraulic pressure may beharvested during pressure testing of the subsea well system 100. Forexample, with additional reference to FIG. 1, tubing hanger 121 islanded in wellhead 136 on landing string 132. Tubing hanger 121 (i.e.,hydraulically actuated device) is set in wellhead 136, for example byoperation of control system 12 and utilizing hydraulic power fromhydraulic power unit 14. A pipe ram 138 is closed, for example on aslick joint 122 of subsea tree 120, creating closed annulus pressurezone 18. Valve 30 may be opened and fluid 26 from fluid system 5 can besupplied though BOP access line 144 to annulus pressure zone 18 topressure test the seal of tubing hanger 121. The pressure in closedannulus pressure zone 18 can be communicated through port 20 to in-riserhydraulic power recharging system 10 to recharge the hydraulic powerexpended for example to set tubing hanger 121. Pressure in annuluspressure zone 18 can be relieved, for example, by opening pipe ram 138and valve 32 in BOP access line 146 in the depicted embodiment.

FIG. 4 is a schematic diagram of an example of an in-riser hydraulicpower recharging system 10 according to one or more embodiments. Withreference also to FIGS. 1-3, in-riser hydraulic power recharging system10 provides hydraulic communication between the created annulus pressurezone 18 and the closed loop hydraulic control circuit 38, 42 extendingfrom a hydraulic accumulator 34 (i.e., supply accumulators) through asupply conduit 38 to a hydraulically actuated device generally denotedby the numeral 40, and from the hydraulically actuated device 40 througha return conduit 42 to hydraulic reservoir 36. Hydraulically actuateddevice 40 includes without limitation tubing hanger 121, latch 126, andsafety valves 128, 130. For example, to actuate hydraulically actuateddevice 40 hydraulic pressure and fluid 44 is communicated from ahydraulic supply accumulator 34 through supply conduit 38 tohydraulically actuated device 40. Upon actuation of hydraulicallyactuated device 40, hydraulic fluid 44 is communicated fromhydraulically actuated device 40 through return conduit 42 to hydraulicreservoir 36.

In-riser hydraulic power recharging system 10 includes a hydraulicrecharging circuit generally denoted by the numeral 46 in hydrauliccommunication between annulus pressure zone 18 and closed loop hydrauliccontrol circuit 38, 42. The hydraulic power recharging system 10illustrated in FIG. 4 may be described as a primary recharging system.According to embodiments, hydraulic recharging circuit 46 includes oneor more hydraulic intensifiers 48. For example, with reference to FIG.4, an intensifier 48 is disposed in hydraulic conduit 22 between annuluspressure zone 18 and closed loop hydraulic control circuit 38, 42.Hydraulic pressure applied at annulus pressure zone 18 is communicatedto a low pressure side 50 of intensifier 48 to act on piston 52 and urgepiston 52 in a first direction toward high pressure side 54communicating pressurized hydraulic fluid 44 through supply conduit 38to hydraulic supply accumulators 34. In the depicted embodiments, lowpressure side 50 of piston 52 has a larger surface area than highpressure side 54 of piston 52. Upon release of the hydraulic pressureapplied in annulus pressure zone 18, intensifier spring 56 (e.g.,mechanical spring, pressurized fluid spring, mechanical switching valve,etc.) urges piston 52 in the second direction toward low pressure side50 drawing hydraulic fluid 44 from hydraulic reservoir 36 and returnconduit 42 to high pressure side 54 of intensifier 48. According toembodiments, high pressure side 54 of intensifier 48 is hydraulicallyconnected to hydraulic supply conduit 38 through a supply control valve58 (e.g., one-way valve) and similarly high pressure side 54 ishydraulically connected to hydraulic return conduit 42 through a return,or reserve, control valve 59 (e.g., one-way valve). High pressure side54 can include conduit 47 extending between supply one-way valve 58 andreserve one-way valve 59. According to some embodiments, a valve 60 maybe connected between annulus pressure zone 18 and low pressure side 50of intensifier 48 to control communication of hydraulic pressure inannulus pressure zone 18 and hydraulic recharging circuit 46. Theprocess is repeated until the closed loop hydraulic circuit 38, 42pressure range is achieved, for example a hydraulic supply accumulator34 is pressurized to a desired hydraulic pressure level.

An example of a method of operation is now described with reference toFIGS. 1-4. A hydraulically actuated device 40 is operated reducing thehydraulic pressure stored in hydraulic supply accumulators 34. Torecharge the pressure of hydraulic supply accumulators 34 an annuluspressure zone 18 is created in BOP stack 108. Annulus pressure zone 18is created by closing one or more for example by closing one or more ofBOP pipe rams 138 and or annular rams 142. A BOP access line, forexample BOP access line 144 is opened to communicate with annuluspressure zone 18 and communication with the corresponding BOP accessline 146 is closed if necessary. A hydraulic pressure is applied toannulus pressure zone 18, for example, fluid system 5 may be operated tocommunicate fluid 26 and pressure to annulus pressure zone 18. Thehydraulic pressure may be applied to annulus pressure zone 18 solely forthe purpose of operating hydraulic pressure recharging circuit 46 andhydraulic power recharging system 10 or the hydraulic power may beapplied during testing operations. The increasing applied hydraulicpressure in annulus pressure zone 18 is communicated to intensifier 48.The increasing applied pressure operates intensifier 48 to communicatehydraulic fluid 44 in the supply conduit 38 side of hydraulic controlcircuit to hydraulic supply accumulator(s) 34 and to draw hydraulicfluid 44 from the return conduit 42 side of hydraulic control circuit38, 42 into hydraulic recharging circuit 46 and high pressure side 54 ofintensifier 48. When the stroke of piston 52 in the direction from lowpressure side 50 to high pressure side 54 has stopped, hydraulicpressure in annulus pressure zone 18 is relieved, for example, byopening a BOP access line 146 in communication with annulus pressurezone 18. When the hydraulic pressure is relieved from annulus pressurezone 18, spring 56 urges piston 52 toward low pressure side 50 causinghydraulic fluid 44 to be drawn from return conduit 42 and hydraulicreservoir 36 of hydraulic control circuit 38, 42 into hydraulicrecharging circuit 46 at high pressure side 54. The process of buildingand relieving pressure in annulus pressure zone 18 communicated torecharging circuit 46 can be repeated until the desired hydraulicpressure level is achieved in hydraulic supply accumulator(s) 34.Hydraulic recharging circuit 46 is operated in response to applying ahydraulic pressure to annulus pressure zone 18. In accordance to someembodiments, the applied hydraulic pressure includes increasing orbuilding pressure and decreasing or relieving pressure in annuluspressure zone 18.

FIG. 5 illustrates an embodiment of in-riser hydraulic power rechargingsystem 10 using a hydraulic recharging circuit 46 as a secondaryrecharging circuit. For example, with additional reference to FIGS. 1-3,hydraulic power unit 14 may include one or more hydraulic pumps 62 torecharge hydraulic supply accumulators 34. For example, return conduit42 may be connected to an inlet 61 of a hydraulic pump 62 and the outlet63 of hydraulic pump 62 is connected to supply conduit 38 for examplethrough a one-way valve 64. Hydraulic pump 62 may be operated topressurize hydraulic fluid 44 from return conduit 42 and hydraulicreservoir 36 and communicate the pressurized hydraulic fluid 44 tohydraulic supply accumulators 34. In the illustrated embodiment, highpressure side 54 of intensifier 48 is hydraulically connected throughreserve one-way valve 59 to return conduit 42 and hydraulic reservoir 36upstream of inlet 61 to hydraulic pump 62 and high pressure side 54 ishydraulically connected to supply conduit 38 and hydraulic supplyaccumulators 34 through supply one-way valve 58 downstream of outlet 63of hydraulic pump 62. In accordance to embodiments, hydraulic rechargingcircuit 46 can be utilized for example in the same manner as describedwith reference to FIGS. 1-4 to pressurize one or more of hydraulicsupply accumulators 34.

FIG. 6 is a schematic illustration of an in-riser hydraulic powerrecharging system 10 for pressurizing individual hydraulic supplyaccumulators 34 to different pressures levels. For example, in theembodiment illustrated in FIG. 6, the left hydraulic supply accumulator34 is identified specifically as a low pressure accumulator 134 and theright hydraulic supply accumulator 34 is identified specifically as ahigh pressure accumulator 234. For example, and without limitation, lowpressure accumulator 134 may be a 5,000 psi accumulator and highpressure accumulator 234 may be a 10,000 psi accumulator. According toembodiments, hydraulic recharging circuit 46 may comprise a firstintensifier 48 identified specifically as low pressure intensifier 148disposed to hydraulically pressurize (e.g., recharge) low pressureaccumulator 134 and a second intensifier 48 identified specifically ashigh pressure intensifier 248 to pressurize (e.g., recharge) highpressure accumulator 234. For example, low intensifier 148 may be a 5 to1 intensifier and high pressure intensifier 248 may be a 10 to 1intensifier. In the illustrated embodiment, low pressure intensifier 148has a low pressure side 50 in hydraulic communication with annuluspressure zone 18 and high pressure side 54 in hydraulic communicationwith supply conduit 38 and low pressure accumulator 134 through a supplyone-way valve 58 and high pressure side 54 is in hydraulic communicationwith hydraulic reservoir 36 and return conduit 42 through reserveone-way valve 59. Similarly, high pressure intensifier 248 has a lowpressure side 50 in hydraulic communication with annulus pressure zone18 and high pressure side 54 in hydraulic communication with supplyconduit 38 and high pressure accumulator 234 through a supply one-wayvalve 58 and high pressure side 54 is in hydraulic communication withhydraulic reservoir 36 and return conduit 42 through reserve one-wayvalve 59. According to embodiments, each of low pressure accumulator 134and high pressure accumulator 234 can be pressurized (i.e., recharged)in response to the same applied hydraulic pressure at annulus pressurezone 18. For example, applying a hydraulic pressure of 1,000 psi via BOPaccess line 144 to annulus pressure zone 18 operates hydraulicrecharging circuit 46 to pressurize each of low pressure accumulator 148and high pressure accumulator 248 to the respective desired pressurelevel. For example, the applied hydraulic pressure is communicated fromannulus pressure zone 18 to low pressure side 50 of low pressureintensifier 148 causing hydraulic fluid 44 to be drawn from hydraulicreservoir 36 to high pressure side 54 of low pressure intensifier 148and communicated at a pressure of 5,000 psi to low pressure accumulator134 thereby pressurizing low pressure accumulator 134. Similarly, theapplied hydraulic pressure is communicated to low pressure side 50 ofhigh pressure intensifier 248 causing hydraulic fluid 44 to be drawnfrom hydraulic reservoir 36 to high pressure side 54 and communicated atan increased pressure of 10,000 psi to high pressure accumulator 234thereby pressurizing high pressure accumulator 234.

FIG. 7 is a schematic illustration of an embodiment of an in-riserhydraulic power recharging system 10 utilizing a single intensifier 48to charge individual hydraulic supply accumulators 34 to differentpressures. In the illustrated embodiment, the left hydraulic supplyaccumulator 34 is identified specifically as a low pressure accumulator134 and the right hydraulic supply accumulator 34 is identifiedspecifically as a high pressure accumulator 234. Low pressure side 50 ofintensifier 48 is hydraulically connected to annulus pressure zone 18for example through valve 60. Low pressure accumulator 134 ishydraulically connected to high pressure side 54 of intensifier 48through a second valve 66 (e.g., control valve). In this embodiment,second valve 66 is depicted as normally open. High pressure accumulator234 is hydraulically connected to high pressure side 54 of intensifier48 bypassing second valve 66. According to a non-limiting embodiment,low pressure accumulator 134 is a 5,000 psi accumulator, high pressureaccumulator 234 is a 10,000 psi accumulator, and intensifier 48 is a 5to 1 intensifier. In accordance with an embodiment, a first hydraulicpressure is applied at pressure zone 18 and communicated to low pressureside 50 and the corresponding high hydraulic pressure fluid 44 from highpressure side 54 is communicated to both low pressure accumulator 134through open second valve 66 and to high pressure accumulator 234. Forexample, for a first applied hydraulic pressure of 1,000 psi applied viaBOP access line 144 to annulus pressure zone 18 and hydraulic rechargingcircuit 46 is converted by 5 to 1 intensifier 48 to a 5,000 psihydraulic pressure at high pressure side 54 and communicated to both oflow pressure accumulator 134 and high pressure accumulator 234. Applyingthe first hydraulic pressure to pressurize low pressure accumulator 134to the desired pressure level range may include repeating the process ofincreasing and decreasing the first applied hydraulic pressure. Torecharge high pressure accumulator 234 to 10,000 psi, second controlvalve 66 is closed and a second hydraulic pressure of 2,000 psi isapplied through BOP access line 144 to annulus pressure zone 18 and lowpressure side 50 of intensifier 48. The 5 to 1 intensifier 48 convertsthe second applied pressure zone 18 pressure to 10,000 psi andcommunicates the hydraulic pressure to pressurize high pressureaccumulator 234. Once again, applying the second applied pressure mayinclude increasing and decreasing the pressure level in annulus pressurezone 18 multiple times.

A non-limiting example of an in-riser hydraulic power recharging methodis now described with reference to the block diagram depicted in FIG. 8and with additional reference to FIGS. 1-7. An in-riser hydraulic powerrecharging method 300 in accordance to one or more embodiments includescreating 310 an annulus pressure zone 18 in hydraulic communication witha hydraulic supply accumulator 34 through a hydraulic recharging circuit46. Annulus pressure zone 18 may be created in blowout preventer stack108, for example by closing a blowout preventer stack ram 138, 142.Non-limiting examples for creating 310 annulus pressure zone 18 aredescribed above, for example with specific reference to FIGS. 2 and 3.Applying 320 hydraulic pressure to annulus pressure zone 18 may beperformed for example by communicating drilling fluid 26 through BOPaccess line 144 to annulus pressure zone 18. Applying 320 hydraulicpressure to annulus pressure may be solely for the purpose of operatinghydraulic recharging circuit 46 or to accomplish other tasks. Forexample, hydraulic pressure may be applied 320 to annulus pressure zone18 during well testing. According to some embodiments, applying 320hydraulic pressure includes increasing and decreasing the pressure level(e.g., cycling the pressure) in annulus pressure zone 18. In accordanceto one or more embodiments, applying 320 hydraulic pressure may includeapplying a first pressure level and subsequently applying a secondpressure level different from the first pressure level. Depicted method300 includes operating 330 hydraulic recharging circuit 46 in responseto the applied hydraulic pressure. Operating 330 hydraulic rechargingcircuit 46 includes communicating the applied hydraulic pressure fromannulus pressure zone 18 to recharging circuit 46. According to someembodiments, operating 330 may include operating one or more controlvalves 60, 66 while applying 320 the hydraulic pressure. Pressurizing340 the closed loop hydraulic control circuit 38, 42, for examplehydraulic supply accumulator 34, may include increasing the pressurelevel of the applied hydraulic pressure level communicated to hydraulicrecharging circuit 46 and communicating that increased pressure level tohydraulic fluid 44 in closed loop hydraulic control circuit 38, 42 andhydraulic supply accumulator 34. Pressuring 340 may include pressurizingfirst hydraulic supply accumulator, for example a low pressureaccumulator 134, to a first pressure level and pressuring a secondhydraulic supply accumulator, for example a high pressure accumulator234, to a second pressure level higher than the first pressure level. Inaccordance to some embodiments, the low pressure hydraulic supplyaccumulator 134 and the high pressure hydraulic supply accumulator 234may be pressurized 340 substantially simultaneously while applying 320the hydraulic pressure at a first level.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from the invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims, means-plus-function clauses are intended tocover the structures described herein as performing the recited functionand not only structural equivalents, but also equivalent structures.Thus, although a nail and a screw may not be structural equivalents inthat a nail employs a cylindrical surface to secure wooden partstogether, whereas the screw employs a helical surface, in theenvironment unfastening wooden parts, a nail and a screw may beequivalent structures. The term “comprising” within the claims isintended to mean “including at least” such that the recited listing ofelements in a claim are an open group. The terms “a,” “an” and othersingular terms are intended to include the plural forms thereof unlessspecifically excluded.

What is claimed is:
 1. A method for pressurizing a hydraulicaccumulator, comprising: creating an annulus pressure zone by closingrams in a blowout preventer stack, said annulus pressure zone being inhydraulic communication with a hydraulic accumulator through a hydraulicrecharging circuit, the hydraulic recharging circuit having a hydraulicintensifier in communication with a hydraulic reservoir and with ahydraulically actuated device; applying a hydraulic pressure to theannulus pressure zone; operating the hydraulic recharging circuit viashifting of the hydraulic intensifier in response to the appliedhydraulic pressure; pressurizing the hydraulic accumulator in responseto the operating the hydraulic recharging circuit; and shifting thehydraulic intensifier back toward an original position to draw hydraulicfluid from the hydraulic reservoir.
 2. The method of claim 1, whereinthe annulus pressure zone is created in the blowout preventer stack. 3.The method of claim 1, wherein the annulus pressure zone is between atubing hanger and a closed pipe ram.
 4. The method of claim 1, whereinthe applying the hydraulic pressure to the annulus pressure zonecomprises increasing pressure in the annulus pressure zone anddecreasing pressure in the annulus pressure zone.
 5. The method of claim1, wherein the hydraulic pressure applied to the annulus pressure zoneis communicated through a blowout preventer access line.
 6. The methodof claim 1, wherein: the hydraulic accumulator comprises a firsthydraulic accumulator and a second hydraulic accumulator; and thepressurizing the hydraulic accumulator comprises pressurizing the firsthydraulic accumulator to a first pressure and pressurizing the secondhydraulic accumulator to a second pressure different from the firstpressure.
 7. The method of claim 6, wherein the hydraulic intensifier ofthe hydraulic recharging circuit comprises: a first intensifierhydraulically connected between the annulus pressure zone and the firsthydraulic accumulator; and a second intensifier hydraulically connectedbetween the annulus pressure zone and the second hydraulic accumulator.